Intraoperative angiography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs with particular interest to the arteries, veins, and the heart chambers during a cardiac operation procedure.
Intraoperative fluorescence imaging (IFI), may be used to verify tumor removal in oncological pathologies. Use of IFI to assess myocardial perfusion intraoperatively after off-pump cardiac artery bypass graft (OPCABG) surgery has been clinically tested. This procedure may involve the injection of fluorescent tracers into the venous system of the patient during the surgery, and excitation of the tracers with a near-infrared laser light source. Currently, IFI system may be used for assessment of the grafts. However, since the photons emitted in fluorescence applications are highly absorbed in tissue (unlike gamma photons), the IFI signals are reduced when the target is covered by a layer of tissue (intramyocardial arteries).
High frequency handheld ultrasound systems have been investigated for use in OPCABG to detect the intramuscular left anterior descending (LAD) coronary arteries during OPCABG. This method may provide poor image quality for on-pump cardiac artery bypass graft (CABG) and coronary arteries other than the LAD during OPCABG, if at all accessible to the system.
Conventional, as well as hand held diagnostic nuclear imaging, may identify radionuclide distribution in a subject, such as a human patient. Typically, one or more radiopharmaceuticals or radioisotopes are injected into the subject's blood system. This results in a relatively high whole body radiation dose. Even specifically binding tracers that concentrate in specific areas within the tissue may travel to all tissues of the patient's body. A typical minimum effective radiation dose may range from 2.2 mSv to more than 30 mSv, depending on the radionuclide tracer used for the imaging procedure
In conventional open chest CABG surgery, the patient's heart beat may be stopped while the circulation and oxygenation of blood is provided by an extracorporeal cardiopulmonary bypass using a heart-lung machine. This state is known as cardioplegic arrest. During surgery, two separate blood circulations are maintained. A systemic blood circulation delivers oxygenated blood to the body tissues. Cardioplegia fluids are delivered by a heart-lung machine, for example, that oxygenates the heart muscle, and that delivers nutrients and various drugs to the heart tissue, such as potassium to induce cardiac arrest. The result is a small circulation with a substantially small volume of blood oxygenating the heart and that is ready for delivering any substance to the heart vasculature, such as radiotracers used for imaging.
In each of these cases, imaging of small blood vessels in the heart, such as intramyocardial coronary arteries, may be useful for accessing the levels of cardiac dysfunction such as ischemia. However, many of the imaging techniques, as described above, used to detect the radiation from injected radiotracers may lack the imaging resolution needed for imaging these small blood vessels. Thus, these techniques may be incapable of determining if blood flow is improved in these small blood vessels, for example, so as to assess the effectiveness of the therapeutic treatments such as OPCABG and/or CABG.